Energy balance in the dssat-csm-cropgro model

Authors: CUADRA, SANTIAGO - Brazilian Agricultural Research Corporation (EMBRAPA); Kimball, Bruce; BOOTE, KENNETH - University Of Florida; SUYKER, ANDREW - University Of Nebraska; PICKERING, NIGEL - Washington State University

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2020
Publication Date: 2/15/2021
Citation: Cuadra, S.V., Kimball, B.A., Boote, K.J., Suyker, A.E., Pickering, N. 2021. Energy balance in the dssat-csm-cropgro model. Agricultural and Forest Meteorology. 297. Article 108241. https://doi.org/10.1016/j.agrformet.2020.108241.
DOI: https://doi.org/10.1016/j.agrformet.2020.108241

Interpretive Summary: Crop growth models that simulate effects of weather, soils, and management practices on crop growth and yield are valuable tools for assisting today’s farmers in their management decisions, as well as for developing strategies to cope with future global change. However, most “grow” their crops at air temperature rather than at the crop’s vegetation temperature, which can differ from air temperature by several degrees, especially for irrigated agriculture. If an accounting is made of all the significant energy flows to and from a crop canopy, it is possible to compute the crop’s temperature, as well as its water use. Such code was written for the DSSAT-CSM-CROPGRO model – one of the most popular and widely used models – more than two decades ago, yet this feature of the model has been ignored and not used for these many years. For this paper, we re-established links within the code and made some improvements to resurrect this “energy balance” feature, and we tested it against eddy covariance data collected over soybean at Mead, Nebraska. Comparisons with these data showed that generally the resurrected and improved model can simulate the energy flows, including water use, well. Therefore, the improved CROPGRO model has promise for helping to improve present and future crop management practices, which will help all consumers of food and fiber.

Technical Abstract: One potential way to improve crop growth models is for the models to predict energy balance and evapotranspiration (ET) from first principles, thus serving as a check on “engineered” ET methodology. In this paper, we present new implementations and the results of an energy balance model (EBL) developed by Jagtap and Jones (1989) and then implemented in DSSAT’s CROPGRO (CG-EBL) model by Pickering et. al. (1995) as a linked energy balance-photosynthesis model that has not been field-tested until now. The energy balance code computes evapotranspiration and other energy balance components, as well as a canopy air temperature, based on three sources (sunlit leaves, shaded leaves, soil surface). Model performance was evaluated with measured biomass and energy fluxes from two sites in Nebraska, namely, the US-Ne2 irrigated maize-soybean rotation field and the US-Ne3 rainfed maize-soybean rotation field, which are part of the Ameriflux eddy covariance network (https://ameriflux.lbl.gov/sites). After implementing new aerodynamic resistances and the stomatal conductance model of the Ball–Berry–Leuning, crop growth, evapotranspiration and soil temperature were simulated well by the EBL model. The EBL improved ET predictions slightly over the often-used FAO56 method [Penman–Monteith (Allen et al., 1998)] for 4 of the 5 years evaluated for both irrigated and rainfed conditions. Further, a significant improvement was achieved using EBL for the simulation of soil temperature at the various depths compared to STEMP, the original subroutine in DSSAT for simulating soil temperature. Compared to the other available DSSAT methods, the EBL explicitly simulates the impacts of crop morphology, physiology and management on the crop’s environment and energy and mass exchange, which in turn directly affect the water use and irrigation requirements, phenology, photosynthesis, growth, sterility, and yield of the crop.